I winterize the water system and sanitary systems myself and have had no issues. I was thinking of doing the Kohler 6.5 myself this year, engines I can't do, as I have to run the boat up the river to its winter storage place, so the Marina does this.
Please advise on what I tghink is a proper procedure:

The genset has a heat exchanger. I was going to CLOSE the seacock, and open the strainer to allow what sea water is in to drain out, with my transfer pump, it is a straight shot from seawater pump to strainer, so I am confident that will empty the sea water. Then I was planning on taking the hose off of the raw water pump for genset, and putting a short piece of hose on it, start the genset and flush out the heat exchanger with fresh water. Lastly, I would pour antifreeze (-100 stuff) into the hose with the unit running until I got a steady flow out the side exhaust port.

Sound reasonable?